In alkali chloride electrolysis to produce an alkali hydroxide and chlorine by electrolyzing an aqueous solution of an alkali chloride (such as sodium chloride, potassium chloride or lithium chloride), an ion exchange membrane having a layer made of a fluorinated polymer having carboxylic acid type functional groups on the cathode side and having a layer made of a fluorinated polymer having sulfonic acid type functional groups on the anode side, is used as a diaphragm (see e.g. Patent Documents 1 and 2).